Blanching at the stench of urine, I stumble up pitch-black, uneven steps to the top floor, which seems to be a rooftop on which someone has constructed shacks out of brick, asbestos and plastic. A shaft of light from a street lamp falls past tenuous bamboo railings onto a figure in a glittering white sari. She crouches on the bare brick floor by the roof's edge, holding a mirror in one hand and a lipstick in another, using the light to make up. Older residents of the brothel, who expect no clients, crowd into a tiny room to tell me their stories. "I've spent my life in this hell," says Pushpa Adhikari, an ancient woman with sad eyes who was sold into sexual slavery at the age of nine. The others demur: thugs used to terrorize the brothels with nightly rapes and murders, but now that the prostitutes are united the hoodlums keep their distance. "It used to be hell--now it's heaven," corrects one woman, and even Adhikari nods.

Freeing the brothels from terror is merely a side effect of the Sonagachi project, an HIV intervention program named after the red-light district of Kolkata (formerly Calcutta) where it began. Rural poverty forces millions of Indian men to migrate to urban centers in search of a livelihood; there they visit brothels, pick up the AIDS virus and take it back to their wives. Truck drivers also infect prostitutes along the major highways. India already harbors at least five million cases of HIV--the most in the world after South Africa--but it is too poor, and its health infrastructure too weak, to permit reliance on drugs. Only if prostitutes cease to acquire and transmit the virus can the epidemic be contained, and Smarajit Jana, a public health scientist, has found a way to accomplish that.

"I strongly believe that for a program to succeed, the subjects have to adopt its goals as their own," he explains. They have: the sex workers run the HIV program themselves. Jana persuaded them to form a growing collective that now includes 60,000 members pledged to condom use. It offers bank loans, schooling for children, literacy training for adults, reproductive health care and cheap condoms--and has virtually eliminated trafficking of women in the locale. Best of all, the project has kept the HIV prevalence rate among prostitutes in Sonagachi down to 5 percent, whereas in the brothels of Mumbai (Bombay) it is around 60. Other sexually transmitted diseases are down to 1 percent. Jana now works with CARE in Delhi, assisting other social workers in similarly transferring their HIV prevention programs to the people they serve. Such community-led interventions have become integral to the Bill and Melinda Gates Foundation in its five-year, $200-million effort to combat AIDS in India.

An unassuming man with flyaway hair and a ready smile, Jana, who is now 53, went through medical school in Kolkata in the 1970s. There he organized students to collect leftover medicines and visit slums to treat the inhabitants. Medical school in India is highly subsidized, so "we felt very strongly that we were morally responsible" to give something back, Jana recalls. They campaigned and litigated against hazardous medical products, getting two dozen of them recalled. When, instead of aiming for a lucrative private practice, Jana specialized in public health and went off to run a rural clinic, his parents were horrified.

At the clinic, Jana observed that if a woman had undergone a tubectomy, for which she had received money from a population-control program, she invariably blamed any subsequent health problems on it. Circumstances having forced her into the operation, she resented it and influenced others against it. "In the short term, you can get results with such coercive methods," Jana realized, "but in the long term, the program will fail"--as, indeed, the sterilization effort did. To truly succeed, one needed not only informed consent but heartfelt consent, which meant that one first had to understand what made someone tick.